1. Field of the Invention
The present invention relates to a compressor bearing used for a compressor body and a pulley mechanism transmitting a driving force to the compressor body, and a compressor component.
2. Description of the Background Art
To increase the life of a rolling bearing incorporated into a compressor with a pulley mechanism (referred to as a compressor bearing hereinafter), a thermal treatment is performed. Conventionally, for example, in quenching the components they are heated in an ambient RX gas with ammonium gas further introduced therein to carbo-nitride their surface layer portion. This carbonitriding process can harden the surface layer portion and generate retained austenite in a microstructure to provide increased rolling contact fatigue life (Japanese Patent Laying-Open Nos. 11-101247 and 8-4774).
The above-mentioned carbonitriding process for the compressor bearing components is a process to diffuse carbon and nitrogen. This requires a high temperature maintained for a long period of time.
When bearing components are held at a high temperature for a long time, an austenite grain is coarsened resulting in reduced toughness and thus brittle steel. This leads to reduced crack strength.
In addition, the coarsened austenite grain results and increased anti-crack strength is hardly obtained. Furthermore, as more austenite is retained, secular dimensional variation rate increases.
The carbonitriding process of diffusing carbon and nitrogen requires that bearing components should be maintained at a high temperature for a long period of time. This results in a coarsened structure and imposes a limitation on increasing a fracture stress value, which corresponds to anti-crack strength.
On the other hand, there are demands on the compressor bearing with a pulley mechanism (1) to secure an increased life time against rolling fatigue, (2) to improve anti-crack strength, and (3) restrain an increase in secular dimensional variation rate.
In conventional techniques, to achieve such mechanical characteristics, compositions are adjusted in designing steel alloys. However, a raw material of a special alloy component is hardly available thereby leading to high costs.
A future compressor bearing with a pulley mechanism is requested to have a mechanical characteristic that allows for the use under a higher load and at a higher temperature than the conventional bearings in order to accommodate an environment of a higher load and higher temperature.
Therefore, the above-described compressor bearing needs to be strong and requires (1) a long rolling contact fatigue life, (2) a high anti-crack strength, and (3) dimensional stability enhanced by restraining an increase in secular dimensional variation rate.